Projection system and display apparatus for compressing and expanding aspect ratio of a picture

ABSTRACT

A projection system for pictures and a projection display apparatus which are designed to improve the luminance and contrast of a magnified picture on a projection screen by increasing the luminous flux projected within the effective size of projection optical systems. The projection display apparatus has a picture compressions device for compressing the aspect ratio of the source picture formed on the face plate panel (PNL) of a projection cathode-ray tube (PRT) or a liquid crystal panel (LCP) to make it substantially 1 and an optical system for extending a picture (EXT) for extending the source picture having the same aspect ratio as that of the original picture. With this construction, the whole luminous flux passing the effective size of the projection optical system is maximized with the effect of improving the luminance and contrast of the magnified pictured projected onto the projection screen.

This application is a continuation of application Ser. No. 07/873,011,filed Apr. 24, 1992, now U.S. Pat. No. 5,386,252.

BACKGROUND OF THE INVENTION

The present invention relates generally to projection systems forpictures and projection display apparatus, and more particularly to aprojection system for pictures which is capable of improving theluminance and contrast of the magnified picture projected onto aprojection screen and a projection display apparatus therefor.

A conventional projection display apparatus of the sort described aboveis constructed so that the source picture formed on the face plate panelof a projection cathode-ray tube or a liquid crystal panel is projectedonto a projection screen by means of an optical system for magnifyingwhose magnifications in both horizontal and vertical directions areequal.

In the projection display apparatus using such a projection cathode-raytube, the face plate panel is bombarded with a electron beam having agreat current to form a Source picture and the magnifying projectionoptical system is used to project the source picture onto the projectionscreen.

In order to intensify the luminance and contrast of the pictureprojected onto the screen by strengthening the luminance of the sourcepicture formed on the face plate panel, a current density needsincreasing while the spot size of the electron beam for use in formingthe source picture is decreased as disclosed in Japanese PatentLaid-Open No. 561/1979. However, the temperature of the face plate panelis caused to rise because of the bombardment of the electron beam at thelarge current and this results in reducing the light emission efficiencyof the fluorescent material and consequently reducing the luminance andcontrast of the magnified picture projected onto the projection screen.Moreover, the projection cathode-ray tube and the magnifying projectionoptical system, when positioned close to each other, may admit ofreflection of light therebetween, thus allowing a reduction in theluminance and contrast of the picture on the screen likewise.

Attempts have been made to solve the foregoing problems; in the case ofthe former problem, for instance, Japanese Patent Laid-Open No.90628/1973 discloses the provision of a cooling construction for a faceplate panel so as to prevent its temperature from rising.

As what was intended to solve the latter problem, moreover, JapanesePatent Laid-Open No. 194234/1983 discloses the provision of a reflectionpreventive medium between a face plate panel and an optical system.

Further, the Television Society Journal `Projection Large ScreenDisplay,` pp 164-, February 1991, for instance, may be quoted as whatdiscloses a general system configuration relative to a projectiondisplay of the sort stated above.

When the prior art projection cathode-ray tube is used to deal with apicture whose vertical length is different from horizontal length,particularly when a picture like a high-vision picture having anextremely high aspect ratio of a horizontal to vertical ratio isreferred to as "an aspect ratio" is projected, the source picturegenerated on the face plate panel of the projection cathode-ray tubebecomes oblong.

As the source picture formed on the face plate panel is restricted bythe size of its long side (generally the size in the horizontal orlateral direction), an area of the picture within the (effective) sizethat can be covered by a projection optical system relatively decreasesfor higher aspect ratio and this results in reducing the luminance andcontrast of the picture projected onto a projection screen as the wholeluminous flux on the screen abates. This problem arises not only whenthe projection cathode-ray tube is used as a means for generating thesource picture but also when a means for generating a picture such as aliquid crystal panel is employed.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a projection system forpictures which is capable of improving the luminance and contrast of thepicture projected onto a projection screen by making as large aspossible an area of a source picture to be covered by the effective sizeof a projection optical system and increasing the whole luminous flux onthe projection screen while keeping constant the size that can becovered by the projection of the projection optical system, and aprojection display apparatus therefor.

In order to accomplish the object by means of the projection displayapparatus using projection cathode-ray tubes or liquid crystal panelsaccording to the present invention, an oblong picture having fourstraight sides, shorter or longer in the vertical direction than in thehorizontal direction (the aspect ratio being 4:3 for the standardtelevision system; and 16:9 for the high-vision system) is reduced insuch a way that the aspect ratio becomes equalized or substantiallyequalized so that the picture is projected onto the face plate panel ofthe cathode-ray tube or onto a means for generating a source picturesuch as a liquid crystal panel. The source picture is magnified by theprojection optical system to the original picture frame size (at theoriginal aspect ratio) in order for the picture to be projected onto theprojection screen. This system described above has been implemented intoa projection display apparatus.

In the projection display apparatus using projection cathode-ray tubes,the shape of an electron beam spot on the face plate panel shouldpreferably be oval in that the source picture is longer in a directionin which the compression ratio is small (generally in the verticaldirection). In the projection display apparatus using a panel typedisplay element such as a liquid crystal display element (hereinaftercalled a liquid crystal panel), on the other hand, the liquid crystalpanel should preferably be rectangular in that the shape of a pixel onthe liquid crystal panel is longer in the vertical direction (adirection in which the compression ratio is small). Moreover, a sourcepicture to be formed on the face plate panel of the cathode-ray tube orthe liquid crystal panel should preferably be square substantially at anaspect ratio of 1.

The ratio of the horizontal length to the vertical length of the ovalelectron beam spot on the projection cathode-ray tube or of therectangular cell on the liquid crystal panel on which the source pictureis formed should preferably be set so that the above ratio conforms tothe ratio of the vertical length to the horizontal length of theoriginal picture.

More specifically, in a projection system for pictures which comprisesmeans for generating source pictures, projection optical systems andprojection means, and is used for projecting onto the projection meansthe magnified source picture formed on the means for generating sourcepictures by means of the projection optical systems according to thepresent invention, the source picture is formed on means for generatinga source picture with the aspect ratio of the original picture as whatis made different so as to conform substantially to an aspect ratio of 1and the source picture thus formed is projected onto the projectionmeans after being magnified by the projection optical system to theaspect ratio of the original picture. A projection display apparatuscomprising the projection cathode-ray tubes having face plate panels,the projection optical systems for projecting the magnified sourcepictures formed on the face plate panels of the projection cathode-raytubes and the projection screen, is characterized by a picturecompression means for forming the source picture on the face plate panelof the projection cathode-ray tube with the aspect ratio of the originalpicture as what is made different so as to conform substantially to anaspect ratio of 1 and optical systems for extending pictures which areused for projecting on the projection screen the source pictures formedon the face plate panels with the source picture formed thereon as theaspect ratio of the original picture. The optical system for extending apicture is made an optical lens provided on the projection screen sideof the projection optical system or otherwise a convex mirror providedbetween the projection optical system and the projection screen.

The shape of the electron beam spot on the face plate panel iscompressed at a compression ratio corresponding to the compression ratioin the direction of compression of the original picture.

A projection display apparatus comprising a light source lamp, liquidcrystal panels having each a number of pixel cells in the form of amatrix, projection optical systems for projecting the magnified sourcepictures formed on the liquid crystal panels and a projection screen,further comprises according to the present invention a picturecompression means for forming the source picture on the liquid crystalpanel with the aspect ratio of the original picture as what is madedifferent so as to conform substantially to an aspect ratio of 1 and anoptical system for extending a picture which is used for projecting onthe projection screen the source picture formed on the face plate panelwith the source picture formed on the liquid crystal panel as the aspectratio of the original picture. Each of the pixel cells constituting theliquid crystal panel is compressed into a shape at a compression ratiocorresponding to the compression ratio in the direction of compressionof the original picture.

As the aspect ratio (the ratio of the horizontal size to the verticalsize) of the picture formed by the means for generating a source pictureis set substantially at 1, the area of a rectangular picture internallytouching the effective circumference of a circular projection opticalsystem is maximized. Therefore, the whole luminous flux projected on theprojection screen has a maximum value, whereby the luminance andcontrast of the picture on the projection screen are improved.

Moreover, as the electron beam spot on the face plate panel of theprojection cathode-ray tube is compressed into a (e.g., vertically longoval) shape in the same direction as that of compression of the size ofthe original picture or as the pixel cell on the liquid crystal panel iscompressed into a (e.g., vertically long rectangular) shape in the samedirection as that of compression of the size of the original picture, itmay be extended by the optical system for extending a picture to theoriginal aspect ratio. Consequently, the balance between the horizontaland vertical resolutions of the magnified picture projected on theprojection screen can be maintained satisfactorily.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an optical system configuration illustrating a projectionsystem for pictures and a projection display apparatus as a firstembodiment of the present invention.

FIG. 2 is a schematic elevational view of an exemplary back projectiontelevision receiver incorporating a projection cathode-ray tubeaccording to the present invention.

FIG. 3 is a schematic sectional side elevation of the back projectiontelevision receiver shown in FIG. 2.

FIG. 4 is a top view of the principal part of a color picture projectionapparatus using a projection cathode-ray tube as a second embodiment ofthe present invention.

FIG. 5 is a schematic sectional side elevation of a back projectiontelevision which is similar to what is shown in FIG. 3 and has theconstruction of FIG. 4.

FIGS. 6A and 6B are diagrams illustrating the size of each sourcepicture formed on the face plate panel of a projection cathode-ray tubeand the shape of each electron beam spot in the central part of thescreen.

FIG. 7 is a schematic perspective view of an exemplary optical systemfor horizontal magnifying EXT as the optical system for extending apicture shown in FIG. 1.

FIG. 8 is a diagram illustrating an exemplary overall optical system asa third embodiment of the present invention.

FIG. 9 is a diagram illustrating an exemplary overall optical system asa fourth embodiment of the present invention.

FIGS. 10A and 10B are diagrams illustrating the size of each liquidcrystal panel for use in forming a source picture and the shape of eachpixel cell.

FIG. 11 is a partial sectional view illustrative of the construction ofa projection cathode-ray tube for use in the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to the accompanying drawings, embodiments of the presentinvention will subsequently be described in detail. In the accompanyingdrawings, reference characters denote the following:

rPRT . . . projection cathode-ray tube for red, gPRT . . . projectioncathode-ray tube for green, bPRT . . . projection cathode-ray tube forblue, PNL . . . panel (face plate panel), CMP . . . picture compressionmeans, LNS . . . projection lens, EXT . . . optical system forhorizontal magnifying, CPL . . . coupler, EXTM . . . mirror forhorizontal magnifying, Lh . . . horizontal length of picture, Lv . . .vertical length of picture, D . . . diagonal size of picture, BM, BM' .. . shape of electron beam spot on face plate panel, dh . . . horizontalsize of electron beam, dv . . . vertical size of electron beam, x . . .horizontal direction, y . . . vertical direction, z . . . direction ofoptical axis, M . . . mirror, DM . . . dichroic mirror, DP . . .dichroic prism, LCP . . . liquid crystal panel, LM . . . lamp, CL . . .condenser lens, C, C' . . . pixel cell, ah . . . . horizontal length ofpixel cell, av . . . vertical length of pixel cell, 1 . . . projectionscreen, 2 . . . mirror.

A projection system for pictures is generally so constructed that itemploys projection cathode-ray tubes, projection liquid crystal panelsor the like as means for generating pictures, arranges to position themeans for generating pictures with a predetermined distance apart from aprojection screen, and uses optical systems for magnifying sourcepictures formed on the respective means for generating pictures andprojecting them on the projection screen.

FIG. 11 is a partial sectional view illustrative of the construction ofa projection cathode-ray tube for use in an embodiment of the presentinvention and particularly of a projection cathode-ray tube of acomposite condensing type which simultaneously uses an electromagneticlens and an electrostatic lens.

As shown in FIG. 11, an electron gun GUN for emitting, controlling,accelerating and condensing electron beams BEM is accommodated in theneck portion NCK of a glass bulb BLB and a monochromatic face platepanel SRN is deposited and formed on the inner face in the panel portionPNL, that is, on the front surface of the glass bulb BLB. The projectioncathode-ray tube PRT is thus constructed.

A deflection yoke DY for deflecting the electron beams BEM emitted fromthe electron gun GUN in the horizontal and vertical directions is fittedto the circumference of the funnel portion FNL of the glass bulb BLB tomake the whole face plate panel SRN luminous. Moreover, a convergenceyoke CY for correcting the misconvergence of the picture sequentiallyreproduced in the projection cathode-ray tube PRT for each color, acentering magnet BCM for regulating the free spot position of theelectron beam BEM, and a focus magnetic MFM for forming anelectromagnetic lens MFL for condensing the electron beams BEM arefitted to a position adjacent to the neck side of the deflection yokeDY.

In addition, a beam alignment magnet BAM for correcting the center axisof the electromagnetic lens MFL formed by the focus magnet MFM and thepassage axis of the electron beam BEM is fitted to the outer peripheryof the neck portion in which the electron gun GUN is accommodated.

The aspect ratio of the source picture formed on the face plate panel ofthe projection cathode-ray tube can be set as desired by the deflectionwaveform applied to the deflection yoke DY or a picture signalprocessing circuit.

Further, the shape of the electron beam spot on the face plate panel canbe controlled by controlling the construction of the electrodes of theelectron gun, the electromagnetic field or magnetic field to be applied.

Although the mainstream of use is for existing projection displayapparatus to be equipped with the projection cathode-ray tubes PRT,those which employ liquid crystal display panels in place of suchcathode-ray tubes as means for generating source pictures have alsorecently been put to practical use.

The aspect ratio of the source picture formed on the liquid crystalpanel may structurally be set as that of the liquid crystal cell of theliquid crystal panel itself.

A detailed description will subsequently be given of each embodiment ofthe present invention in the form of what employs the projectioncathode-ray tubes and the liquid crystal panels as means for generatingsource pictures.

FIG. 1 is an arrangement plan of an optical system with a projectionsystem for pictures and a projection display apparatus as a firstembodiment of the present invention.

In FIG. 1, rPRT denotes a projection cathode-ray tube for red, gPRT aprojection cathode-ray tube for green, and bPRT a projection cathode-raytube for blue. A projection screen 1 is disposed on the center axis ofthe projection cathode-ray tube for green gPRT opposite to a face platepanel PNL with a predetermined distance apart therefrom.

There are also installed projection optical systems, that is, projectionlens systems LNS in front of the respective face plate panels PNL of andalong the respective center axes of the projection cathode-ray tubesrPRT, gPRT, bPRT. Each of the monochromatic pictures (r: red, g: green,b: blue) formed on the face plate panels PNL of the projectioncathode-ray tubes rPRT, gPRT, bPRT are condensed and magnified by therespective projection lens systems LNS before being projected onto theprojection screen. The three colors are synthesized and superposed onthe screen to provide a color picture.

In FIG. 1, a picture compression means CMP is used for compressing anoriginal picture on the face plate panel in such a way that the aspectratio (the ratio of the vertical size to the horizontal size) of thepicture substantially becomes 1. Systems for horizontal magnifying rEXT,gEXT, bEXT as optical systems for extending pictures constitute meansfor extending the source pictures formed on the face plate panels PNL inthe horizontal direction to make each source picture what has the sizeof the original picture.

With this projection display apparatus thus constructed, it is possibleto make reproducible a picture having size, luminance and contrast fargreater than those attainable from an imaging apparatus such as a directviewing television.

As an example of the projection display apparatus, a home projectiontelevision of the sort described above is now widely in use. However,such a television set is desired to be made more compact (thinner) asthe picture offered is large in size.

FIG. 2 is a schematic elevational view of an exemplary back projectiontelevision receiver (hereinafter simply called `back projectiontelevision`) incorporating projection cathode-ray tubes and FIG. 3 is aschematic sectional side view of FIG. 2.

In FIG. 3, the projection lenses LNS are coupled via the respectivecouplers CPL to the projection cathode-ray tubes PRT (rPRT, gPRT andbPRT) and disposed in the lower portion of the television set. Picturesreproduced from the projection cathode-ray tubes PRT are condensed andmagnified via the projection lenses LNS, EXT (rEXT, gEXT, bEXT). Thesepictures thus magnified and reproduced are reflected from a mirror 2disposed at an appropriate angle in the upper portion of the televisionset, so that a projection picture is obtained on the projection screen.

FIG. 4 is a side view of the principal part of a color pictureprojection apparatus using projection cathode-ray tubes as a secondembodiment of the present invention.

In FIG. 4, like reference characters correspond like component parts ofFIG. 1, wherein EXTM represents an optical system (optical system forextending pictures) as another means for horizontally extending picturesthat features the present invention.

In this embodiment, use is made of a mirror EXTM having a convex mirrorface in the horizontal direction in place of the optical systems EXT inthe preceding embodiment.

FIG. 5 is a schematic sectional side view of a back projectiontelevision which is similar to what is shown in FIG. 3 and has theconstruction of FIG. 4.

In FIG. 5, one mirror EXTM having a convex mirror face in the horizontaldirection is used to replace the three EXT (though consisting of threeof rEXT, gEXT, bEXT, only one EXT is shown in FIG. 3, since FIG. 3 is asectional side view of FIG. 2). Even with this construction, it ispossible to form an optical system for horizontally extending pictures(i.e., an optical system for extending pictures).

The television which incorporates the projection cathode-ray tubesutilizing the back projection as described above is advantageous in thatit can be made compact since the projection distance is shortened withthe effect of reducing the depth of the television set.

FIGS. 6A and 6B are diagrams illustrating the size of each sourcepicture formed on the face plate panel of a projection cathode-ray tubeand the shape of each electron beam spot in the central part of thescreen: 6A illustrates the source picture formed on the face plate panelof the projection cathode-ray tube in the prior art and the beam spotconfiguration at the center of the screen; 6B the source picture formedon the face plate panel of the projection cathode-ray tube under thesystem according to the present invention and the beam spotconfiguration at the center of the screen.

Assuming the projection lenses in FIGS. 6A and 6B are similar, thediagonal sizes of the pictures that can be projected thereby becomeequal. The ratio of the width to the height of the picture in thestandard television system differs from the ratio in the high-visionsystem; namely, the ratio of the width Lh to the height Lv in the formeris 4:3, whereas the ratio of the width Lh' to the height Lv' in thelatter is 16:9.

In the prior art projection optical systems, the source picture shown inFIG. 6A is projected onto the projection screen at an equalmagnification in the horizontal direction (in the direction of width)and in the vertical direction (in the direction of heigth Lv). In theprojection system according to the present invention, on the other hand,the ratio of the height Lh' to the width Lv' is substantially 1 as shownin FIG. 6B. In the prior art projection optical system, since thepicture compressed in the horizontal direction is formed on the faceplate panel before being projected onto the projection screen, thepicture projected thereon is compressed in the horizontal direction.

In this embodiment of the present invention, the source picture formedon the face plate panel of the projection cathode-ray tube is projectedonto the screen in such a way that the horizontal size is extended byEXT or EXTM to an extent greater than what is applicable to the verticaldirection to make its dimensions proportionally equal to those of theoriginal.

As shown in FIG. 6A, moreover, though the electron beam spot on the faceplate panel is set circular in the prior art, it is made vertically longoval in proportion to the compression ratio of the picture in theembodiment of the present invention as shown in FIG. 6B. When there isformed a high-vision picture on the face plate panel with the height Lh'and the width Lv' being equal to each other, for instance, it ispreferred to make oval the cathode-ray spot on the face plate panel withthe ratio of the vertical length to the horizontal length thereof(dv/dh) set at 16:9.

In this case, an area S of a picture display portion is given by

    S(a)=Lh×Lv=a/(1+a.sup.2)×D.sup.2               (1)

where D=size in the diagonal direction; and a=ratio of the height to thewidth of the picture.

When a square picture with a=1 and a high-vision picture with a=9/16 arecompared on condition that both diagonal sizes D are equal, forinstance,

    s(1)/s(9/16)=1.17                                          (2)

In other words, the horizontal compression of the picture is seen toincrease by approximately 17% the quantity of light that can beprojected with the same projection lens diameter in the high-visionsystem as shown in FIG. 6B. Even with the addition of the optical systemfor horizontal magnifying, that is, the optical system for extendingpictures EXT (FIG. 1) as will be described below allows for about 4% ofthe quantity of light to be lost at most, the quantity of light can beincreased by over 13%. Moreover, the quantity of light may be reduced tothe least when EXTM (FIG. 4) is employed.

In the case of FIG. 6B, not only the horizontal length but also thedeflection power needed for the horizontal deflection can be reduced bya large margin as compared with what is shown in FIG. 6A. As the powerneeded for the horizontal deflection is generally far greater than whatis needed for the vertical deflection, the system shown in FIG. 6Baccording to the present invention has the secondary effect of reducingpower consumption necessary for deflection.

FIG. 7 is a schematic perspective view of an exemplary optical systemfor horizontal magnifying EXT as the optical system for extending apicture as shown in FIG. 1.

In FIG. 7, x, y and z respectively represent the horizontal and verticalscanning directions and the optical axis of a projection cathode-raytube. The optical system for magnifying is made of glass or plastics andits thickness in the direction of z remains constant without relying onthe direction of y and is set so that it becomes greater as the absolutevalue of x increases. In other words, the optical system is such a lensas made concave in only the horizontal direction (x). The source picturecompressed and formed by the optical system for magnifying in thehorizontal direction on the face plate panel of each PRT (rPRT, gPRT,bPRT) is extended in the horizontal direction in order for a magnifiedpicture having the same aspect ratio as that of the original picture tobe obtained on the screen.

Although the electron beam spot on the face plate panel is verticallylong oval in shape, it becomes circular when it is projected by theoptical system for horizontal magnifying onto the screen, whereby apicture having resolution well balanced vertically and horizontally canbe displayed.

In the back projection display having the mirror shown in FIG. 3, it ispossible to obtain the same effect as what is achievable from theoptical mirror for magnifying which has the convex mirror in thehorizontal direction as shown in FIG. 5.

Moreover, it is also possible to obtain the same effect from thecombination of the optical lens for magnifying of FIG. 7 and the opticalmirror for magnifying of FIG. 4.

The embodiments described above refer to a case where the presentinvention has been applied to the cathode-ray projection display. Adescription will subsequently be given of an application of the presentinvention to a liquid crystal projection display.

To put it simply, the liquid crystal display is equivalent to what hasreplaced a film for a slide projector with a sheet of liquid crystalpanel. In view of resolution as well as brightness, the mainstream ofuse is directed to a projection display apparatus using three liquidcrystal panels corresponding to red, green and blue.

FIG. 8 is a diagram illustrating an exemplary overall optical system asa third embodiment of the present invention. FIG. 9 is a diagramillustrating an exemplary overall optical system as a fourth embodimentof the present invention.

In these embodiments, liquid crystal projection display apparatus arebasically of construction similar to each other as shown in FIGS. 8 and9. Each optical system comprises:

white light source--trichromatic separation system--trichromatic liquidcrystal panel trichromatic synthesizing system--projection lens opticalsystem for extending a picture--projection screen, wherein LM denotes alamp, RF a reflection mirror, DM dichroic mirrors, M reflection mirrors,CL a condenser lens, LCP liquid crystal panels, DP a synthesizing prism,LNS a projection lens, EXT an optical system for extending, SR a screen,CMP a picture compression means for generating pictures on liquidcrystal panels with an aspect ratio of substantially 1.

In this system shown in FIG. 8, white light from the light source M isseparated by the dichroic mirrors into the three primary colors R (red),G (green), B (blue). The picture compression means CMP forms sourcepictures of three primary colors on the liquid crystal panels LCP (rLCP,gLCP, bLCP) with an aspect ratio of substantially 1. The white lightthus separated is made incident on the respective LCP (rLCP, gLCP, bLCP)for modulation and subjected to three color synthesization in thesynthesizing prism DP. The picture thus synthesized is then projected bythe projection lens LNS and the optical system for extending a pictureEXT on the screen SR as a picture of original size.

In FIG. 8, EXTM of FIG. 4 in place of EXT may be used.

FIG. 9 refers to a case where the dichroic mirrors DM in place of thesynthesizing prism of FIG. 8 are used and similarly EXTM in place of EXTis used as the optical system for extending a picture.

FIGS. 10A and 10B are diagrams illustrating the size of each liquidcrystal panel for use in forming a source picture and the shape of eachpixel cell: FIG. 10A illustrates the prior art liquid crystal panel andthe pixel cell; and FIG. 10B illustrates a liquid crystal panelembodying the present invention and the pixel cell.

As shown in FIG. 10A, the ratio of the width (in the horizontaldirection) Lh and the height (in the vertical direction) Lv of thesource pictured formed on the liquid crystal panel in the standardtelevision system is 4:3 and the ratio thereof in the high-vision systemis 16:9. This picture is projected by the projection optical system onthe projection screen at an equal magnification.

In the case of the embodiment of the present invention shown in FIG.10B, on the other hand, the ratio of the width Lh' and the height Lv' ofthe source picture is substantially 1.

Moreover, though the pixel cell is square as shown in FIG. 10A, it ispreferred for the pixel cell C' to be vertically long rectangular inproportion to the compression ratio of the source picture as shown inFIG. 10b. When the width Lh' and the height Lv' of the picture in thehigh-vision system is equal, for instance, the ratio (av/ah) of thevertical length av and the horizontal length ah of the pixel cell shouldpreferably be 16:9 in the shape of a rectangle.

The source picture horizontally compressed is horizontally extended bythe system for horizontally extending EXT or EXTM as the optical systemfor extending a picture to obtain magnified picture on the projectionscreen SR, the magnified picture having the same aspect ratio as that ofthe original picture. Moreover, the image of the pixel cell in the formof a vertically long rectangle becomes square when it is projected bythe system for horizontal magnifying EXT or EXTM on the projectionscreen, so that a picture having resolution well balanced vertically andhorizontally may displayed.

Although a description has been given of the embodiments of the presentinvention with the projection display apparatus for color pictures, thepresent invention is not limited to those described above but applicableto a monochromatic projection display apparatus using one projectioncathode-ray tube or a sheet of liquid crystal panel.

As set forth above, according to the present invention, the area of thepicture that can be projected by the projection lens systems formagnifying is magnifiable so as to maximize the whole luminous flux inthe projection display apparatus using the projection cathode-ray tubesor what uses the liquid crystal panels. In this way, not only theluminance but also the contrast of the picture on the projection screenis improvable.

In addition, the present invention has the effect of reducing the powerconsumption needed for deflection since the length of horizontaldeflection of the electron beam is reducible.

What is claimed is:
 1. A projection system for a picture comprisingmeans for generating source pictures, projection optical system meansfor magnifying the source pictures formed in said means for generatingsource pictures and for projecting the magnified source pictures, and aprojection means for receiving the magnified and projected sourcepictures from the projection optical system means, the means forgenerating source pictures generating source pictures so that an aspectratio of an original picture is varied so as to become closer to 1 ascompared with the original picture, and the projection system formagnifying and projecting the source pictures onto the projection meansincluding means for expanding the source pictures so as to expand theaspect ratio of the source pictures projected onto the projection meansto an aspect ratio substantially corresponding to the aspect ratio ofthe original picture.
 2. A projection display apparatus comprisingprojection cathode-ray tubes each having face plate panels, projectionoptical system means for magnifying and for projecting source picturesformed on the face plate panels of the projection cathode-ray tubes, aprojection screen for receiving the projected and magnified sourcepictures from the projection optical system means, picture compressionmeans for forming source pictures on the face plate panels of theprojection cathode-ray tubes so that an aspect ratio of an originalpicture is compressed and is varied so as to become closer to 1 ascompared with the original picture, and means for expanding the sourcepictures formed on the face plate panels and projected onto theprojection screen to an aspect ratio substantially corresponding to theaspect ratio of the original picture.
 3. A projection display apparatusaccording to claim 2, wherein the means for expanding pictures includesan optical lens provided on the projection screen side of the projectionoptical system means.
 4. A projection display apparatus according toclaim 2, wherein the means for expanding pictures includes a convexmirror provided between the projection optical system means and theprojection screen.
 5. A projection display apparatus according to claim2, wherein the compressing means enables compression of a shape of anelectron beam spot on the face plate panel in a direction of compressionof the source picture.
 6. A projection display apparatus according toclaim 3, wherein the compressing means enables compression of a shape ofan electron beam spot on the face plate panel in a direction ofcompression of the source picture.
 7. A projection display apparatusaccording to claim 4, wherein the compressing means enables compressionof a shape of an electron beam spot on the face plate panel in adirection of compression of the source picture.
 8. A projectioncathode-ray tube for a projection display apparatus comprising electronbeam generation means, a face plate panel, the electron beam generationmeans generating an electron beam spot on the face plate panel for usein generating a source picture having an aspect ratio which is varied soas to be compressed to an aspect ratio closer to 1 as compared with theoriginal picture, the electron beam spot generating means compressingthe electron beam spot on the face plate panel in a direction ofcompression of the source picture.
 9. A projection display apparatuscomprising a light source lamp, liquid crystal panels each having anumber of pixel cells in the form of a matrix, projection optical systemmeans for projecting and magnifying source pictures formed on the liquidcrystal panels, a projection screen for receiving the projectedmagnified source pictures, picture compression means for forming thesource pictures on the liquid crystal panels with an aspect ratio of anoriginal picture which is compressed and varied so as to become closerto 1 as compared with the original picture, and means for expanding thesource picture formed on the liquid crystal panel and projected onto theprojection screen to an aspect ratio substantially corresponding to theaspect ratio of the original picture.
 10. A projection display apparatusaccording to claim 9, wherein the means for expanding includes anoptical lens provided on the projection screen side of the projectionoptical system means.
 11. A projection display apparatus according toclaim 9, wherein the means for expanding includes a convex mirrorprovided between a portion of the projection optical system means andthe projection screen.
 12. A projection display apparatus according toclaim 9, wherein each of the pixel cells of the liquid crystal panel hasa shape which is compressed in the direction of compression of thesource picture.
 13. A projection display apparatus according to claim10, wherein each of the pixel cells of the liquid crystal panel has ashape which is compressed in the direction of compression of the sourcepicture.
 14. A projection display apparatus according to claim 11,wherein each of the pixel cells of the liquid crystal panel has a shapewhich is compressed in the direction of compression of the sourcepicture.
 15. A liquid crystal panel for a projection display apparatuscomprising means for generating a source picture having an aspect ratiowhich is compressed and varied so as to become closer to 1 as comparedwith an original picture, said means for generating including aplurality of pixel cells, each pixel cell having a shape which iscompressed in the direction of compression of the source picture.
 16. Aliquid crystal panel according to claim 15, wherein each pixel cell hasa rectangular shape with a pair of sides of a first length and a pair ofsides having a second length shorter than the first length, the sides ofthe pixel cell of the second length being arranged in the direction ofcompression of the source picture.